Life in Cold Blood (2008) s01e04 Episode Script

ATTENBOROUGH: Whatever your feelings about snakes you cant deny that they have an extraordinary beauty.
Their lack of limbs compels them to deal with lifes problems in ways that are utterly different from ours.
But nonetheless the techniques they have developed are spectacularly successful.
Snakes have one of the simplest of body shapes.
Essentially just a long thin tube.
But they have some remarkably effective ways of getting around.
They can climb a tree simply by embracing its trunk.
Some can flatten their bodies so that they catch the air beneath them and glide.
By hitching up their undersides they can inch themselves forward in a straight line.
A sinuous wriggle enables them to skate across loose sand.
And the same action works equally well in water.
There some swim close to the surface.
Others explore the depths and can stay underwater for hours on end.
One believe it or not can jump.
So leglessness hardly seems such a handicap.
But how did snakes get that way? Well their remote ancestors 1 00 million years ago at the time of the dinosaurs did have legs rather like todays lizards.
Doubtless they were very effective runners.
But some also started to burrow in search of prey.
Below ground legs are a hindrance and over generations they became smaller.
Today burrowing lizards such as skinks seem to be going through the same process.
Many have tiny but recognisable legs.
In others the limbs have become nothing more than functionless flaps.
In this burrowing lizard the process has gone even further.
The animal still has the face of a lizard but its legs have disappeared totally.
It seems that the ancestral snakes went through just such a process way back in geological history some 92 million years ago.
So what did these very first snakes look like? Well the answer can be found in Asian jungles in American woodlands and gardens and even in flowerpots like this.
It may look like an earthworm but actually its a flowerpot snake and its completely blind.
It doesnt need to see because it spends all its life underground.
Ill put it back in its flowerpot and put a flower on top and it will live perfectly happily there in this flowerpot all by itself providing it has enough food.
And theres a surprising amount for a small snake to eat underground.
Ant larvae for example.
These early legless reptiles flourished and remained underground for a long time.
Then around 20 million years ago some of them returned to the surface.
Why? Well by this time the dinosaurs had disappeared and the early mammals had arrived.
They were more nutritious than beetles and worms so the snakes began to catch them instead and became so good at doing so that today they are among the most skilful hunters on Earth.
Here in North America there is a snake that combines its great speed and extraordinary senses in a remarkable hunting strategy we are only just beginning to understand.
A timber rattlesnake.
The morning sun has warmed its body giving it energy and it starts to move.
Its searching for a place where it can conceal itself and wait for prey to come within striking distance.
A little chipmunk.
Its in no danger yet.
The rattlesnake cant move fast enough to chase and catch it.
But small mammals tend to use the same paths as they run over the forest floor and they leave behind a faint trail of scent.
The rattlesnake can detect that scent with its tongue.
It can also locate the warm-blooded chipmunk if its nearby with heat detectors in a pair of pits beneath its eyes.
As it moves it carefully holds its rattle above the ground so it makes no noise.
Its chosen the place to wait at the bottom of this tree stump.
Its coloration matches the ground so closely it needs no further concealment.
Now its just a matter of time.
Seeing a rattlesnake actually catching its prey is a very very difficult thing to observe.
In fact some scientists have watched rattlesnakes for years without seeing that particular crucial moment.
But we have a chance partly because rattlesnakes are ambush hunters so we know exactly where to put up our gear and partly because in that gear weve got the very latest in surveillance equipment.
There are remotely controlled cameras and infrared lights on stands.
And there are motion detectors that will switch on the cameras if anything moves so I neednt wait alongside.
If anything happens the cameras will switch on automatically.
Later I check the replay.
Theres a mouse just along that log.
That obviously came to nothing but the cameras have started recording again and the snake is moving.
Hes checking out the trail with his tongue.
(WHISPERING) See thats exactly where that mouse was running.
Its pitch dark and the mouse clearly has no idea that the snake is there.
But the snake is well aware of the mouse.
Thanks no doubt to those heat-detecting pits.
A snake strikes by suddenly straightening the curve in its neck.
But at the moment the mouse is not within range.
Hes worked out that that is the path along which the mice run and hes getting himself properly adjusted so he can strike it when he next gets a chance.
Now once again waiting.
Thats what snakes are so good at.
(RUSTLING) (ATTENBOROUGH EXCLAIMS) Oh my goodness.
Thats a dead mouse all right.
Slow down that shot and you can see that the snake stabs the mouse just once.
After three convulsive kicks the mouse is dead.
The snake is moving again.
Hes going back now to look for the one that he knows is dead back there.
Where is it? Ah.
Now it looks as though hes really got it.
Thats his dinner and that can last him for three weeks four weeks if necessary.
Rattlesnakes are among the least obtrusive inhabitants of the forests of North America and they are probably far more numerous than many people realise.
Like many other animals snakes use their nostrils to detect smells.
But the most sensitive and accurate information about the world around them comes from that constantly flickering tongue.
With this a snake gathers molecules from the air and carries them back for evaluation to a pair of extremely sensitive organs in the roof of its mouth.
To see of just how important scent can be to a snake Ive come here to Carnac Island just off the coast of Western Australia.
Its home to a large population of highly venomous tiger snakes.
Snakes have been established here for many years but theres something odd about this particular population.
Many of them have damaged heads and some of them are actually blind like this one.
And yet puzzlingly in spite of the fact that theyre blind they all appear to be very well fed.
So how do their heads get damaged? And how in that condition when they cant see anything can they catch all the prey they need? (GULLS CAWING) The snakes of course are not the only inhabitants of the island.
Its also home for a large colony of silver gulls.
The gulls breed throughout the year so their chicks are a source of food for the snakes that never ends.
In fact the snakes eat pretty well nothing else.
But the snakes dont get it all their own way.
The gulls are valiant defenders of their nests and their chicks.
Their stabbing beaks are powerful sharp and strong.
And the gulls always go for the snakes head.
One in 1 0 of the snakes are totally blinded.
Tiger snakes dont have those heat-sensitive pits that rattlesnakes have so these blinded hunters must be guided entirely by their forked tongue.
Its a superb direction-finding device.
The snake can measure the strength of a smell separately on each of the two forks of its tongue.
And if it wishes to follow up a smell then it simply detects the one that has the stronger smell and goes in that direction.
Gull chicks are an ideal prey for a blinded snake because they are programmed to stay on their nests.
Once a snake has located it a chick is doomed.
Snakes it must be admitted have had a bad reputation ever since one appeared in the Garden of Eden.
But in reality even the most aggressive venomous snake will avoid biting a human being if it can.
Why waste venom and risk violent retribution by biting something youre not going to eat? To prevent misunderstanding most venomous snakes warn other animals including human beings to keep out of their way.
(HISSING) (RATTLING) Some snakes do that with sound.
(RATTLING) (HISSING) Others such as cobras give a visual signal by expanding the skin around their heads to form a conspicuous hood.
The threat of a bite is far better defence for a snake than the bite itself.
However there are some snakes that not only use their venom to kill their prey but have also found a way of using it to deter their enemies without even biting them.
This Mozambique cobra has a very special way of doing that.
To demonstrate this with some degree of safety Im going to wear this visor which has been coated with a substance that turns pink in contact with venom.
Lets see what happens.
Its watching me waiting to see if I get too close for its liking.
Venom spurts from its fangs.
As it spits it turns its head from side to side so that the jets have the best chance of hitting my eyes.
(SIGHING) Well I was well and truly sprayed.
Every one of those pink dots is a bead of venom.
And if any one of them had gone in my eye I would be now blind and in extreme pain.
So its a fair warning from that snake to me not to get any closer.
And I dare say if I did I would deserve what I would get which would be a bite.
I have no intention of doing that.
On the other hand some snakes which may appear to be venomous are in reality quite harmless.
These two snakes look very very similar and they both occur here in the southern United States so you are quite likely to meet one or the other here.
One of them however is harmless.
Its called a kingsnake.
The other one is a coral snake and highly venomous.
One bite certain death.
The question is which is which.
Well the key lies in the order of the colour rings.
People here have a local saying Red and black venom lack.
Red and yellow can kill a fellow.
And this one has red and black so I guess thats a kingsnake.
Well see.
So far so good.
Yeah this is a kingsnake.
And what a beautiful snake it is.
A really lovely reptile.
The kingsnake pretends to be venomous when its not.
And theres another snake that pretends to be dead when it isnt.
Snakes being cold-blooded seem to relish the warmth of sun-baked roads and often bask on them.
And as a result of course many get run over.
But things arent always exactly what they seem.
He looks kind of dead but in fact this hog-nosed snake is perfectly all right.
He was just feigning death so that things that might have been interested in a living snake are not.
And whats more (SNIFFING) he has produced rather a remarkable smell.
In fact the smell as it were of rotting flesh.
So maybe he was pretending too that he was not only dead but decomposing.
Very convincing.
Off you go.
The lack of limbs that might seem to us to be such a huge handicap has not stopped snakes from getting around in all kinds of ways and neither does it prevent them from tackling all kinds of meals.
This South African snake has become a specialist in swallowing a particularly awkward mouthful.
Its as accomplished a tree climber as youll find among snakes.
The trees it frequents also hold colonies of masked weaverbirds that suspend their nests from the very tip of the branches.
But the snake is a skilled enough climber to reach them.
The weaverbirds know it well and recognise it as a threat.
(CHIRPING) Its well accustomed to these attacks.
These defenders however are just too determined and it retreats.
But it doesnt give up altogether.
This nest is unguarded.
And this is what the snake is after the eggs.
Each is several times bigger than the snakes head but its jaws are linked by ligaments that are amazingly elastic.
Once the egg is engulfed by the snakes jaws powerful throat muscles push it down its gullet.
Moving X-rays enable us to see exactly whats happening.
Soon the egg reaches a part of the backbone that has downward pointing spines on it.
The snake arches its backbone and then squeezes.
(CRACKING) The shell cracks and the spines on the backbone slit the membrane.
The shell is crushed and rich nutritious yolk flows into the snakes gut.
Then whats left of the shell is regurgitated.
But that of course was a small meal.
Some snakes can tackle much bigger meals than that.
An African rock python one of the biggest of all snakes that can grow over seven metres 20 feet long.
And it is eating an antelope.
It too has an elastic ligament connecting its jaws.
It killed the antelope not with venom but by squeezing it so tightly that it was unable to breathe.
A pythons teeth cant cut or rip.
It has to swallow its prey whole or not at all.
And that may take a day or more.
Without limbs the python cant push the antelope down its throat.
Instead it hitches its jaws diagonally back and forth so that they as it were walk along and over the prey.
Its tube-like body has to stretch so extremely to accommodate such a gigantic meal that its flanks have torn.
But such injuries heal very quickly.
The last of the antelope its hooves are about to disappear.
Gone.
The python will now hide itself away and begin the long process of digestion.
Everything will be dissolved skin hair hooves even horns.
This python will not need to eat again for a year or more.
Wherever its warm and there are animals of some kind there will be snakes to hunt them no matter how difficult the conditions and how awkward the mouthful.
Crabs are in plentiful supply in this mangrove swamp.
There must be 20 on any one of these trees around me.
Theyre all up there waiting for the tide to go out so that they can feed in the mud below.
So there is a meal for a snake here but crabs are not easy to tackle.
Theyre strong armour-plated and covered in spines.
For a snake to tackle one of these would be like me trying to eat a lobster twice the size of my head with my hands tied behind my back.
But there is a snake that knows how to do so.
The crabs cling to the arching struts of the mangroves to keep out of the way of predatory fish but as the tide retreats it becomes safe for them to climb down and start looking for such edible bits as the tide has left behind on the mud.
For the moment theyre safe but soon the sun will set.
Then the snakes will come out of their burrows.
They hunt in the darkness but well be able to follow them with our infrared cameras.
Its now very dark indeed and the snake has to find its way around entirely by touch and smell.
Finding crabs is not difficult.
They swarm all over the mud and the snake is almost bound to encounter one sooner rather than later.
The snake is armed with venom and has short strong fangs which can pierce a crabs shell and stun it.
But that is only half the problem.
Its what it does after it has caught its crab that sets it apart from all other snakes.
It has it.
Now what? The crab is so large that the snake cant swallow it whole.
Slowly and deliberately the snake dismembers the crab.
Each leg contains nutritious muscle.
But the crabs armoured body is simply discarded.
Too difficult.
There are hard-shelled creatures in fresh waters as well as in salt.
Not nearly as many but sufficient number for some snakes to specialise in eating them.
And in the eastern United States many rivers contain crayfish.
Like crabs they have a hard protective shell and they have particularly powerful pincers as well.
The queen snake however eats crayfish and nothing else.
But not just any crayfish.
Its very selective.
Crayfish as they grow shed their armour.
Every three to four weeks a split appears across the back of its shell.
The old shell hinges away and the crayfish hauls itself out and expands its body which is soft.
Its now that the snake has its chance.
A newly moulted crayfish looks much the same but it gives off different chemicals that the snake can detect in the water with its tongue and from some distance away.
It can swallow this crayfish because since it is newly moulted its as soft as a boiled egg.
On occasion snakes have to grapple not only with their prey but with one another in disputes over mates and territory.
This is one of the most formidable the king cobra.
Highly venomous and about four metres 1 4 feet long.
Disputes between rival male king cobras are potentially very dangerous indeed for this species specialises in eating other kinds of snakes.
So they observe strict rules in their fights which prohibit the use of their lethal bite.
Slowed down its a performance full of grace as each contestant strives not to kill his opponent but simply to slam him to the ground.
The defeated male leaves the arena and no harm has been done.
Snakes must also find a way of preventing their courtship from becoming lethal.
This is a Californian kingsnake a male.
He has detected the scent of a female ready to mate.
Like all snakes his eyesight is not good but he can tell from the taste of the air that she is close by.
In fact she is within inches.
For some time the two follow one another nose to tail.
The male begins to caress her sensually jerking and rocking his body as he holds her close.
He has a pair of sexual organs one of which can project to the left and the other to the right.
So no matter which side of him she happens to lie he can reach her.
At last union is achieved.
They may remain together for several hours.
In a few weeks time the female will lay a clutch of eggs.
It may take six or seven weeks for them to hatch but the regions where most snakes live are warm enough for them to develop without any help from the parents.
Cobras lay them on the ground in the leaf litter.
Their soft parchment-like shell is easily split when pushed from within.
The front end of a cobra hatchling is quite capable of giving a bite even while the back end is still within the shell.
Their fangs may be small but since it only takes a tiny drop of cobra venom to kill an animal these youngsters can be as lethal as their parents.
They already have that characteristic warning signal the hood.
Not all snakes lay their eggs.
In some species the female retains them within her body until theyre ready to hatch so she gives birth to live young.
The marshes of northern Argentina home to one of the largest of live-bearing snakes the anaconda.
This is a female and shes heavily pregnant.
Its morning and shes chilly so she moves out of the water and onto the swamp to warm herself in the sun.
Slowly the day begins to warm up.
Now its getting a little too hot for her so she moves back to the water to cool off.
In this way she manages to keep her body close to 29 degrees centigrade perfect for the babies developing within her.
But she wont give birth here and now.
There are caiman around.
At last she finds the quiet pool that she needs.
And her contractions start.
The first of her babies has arrived.
Up it goes to the surface to take its first breath of air.
But there are more babies to come.
Eventually she produces 1 2.
In fact thats quite modest for an anaconda.
They can produce up to 40.
Right from the beginning of their lives theyre totally independent and get no care or protection from their mother.
The anaconda spends so much of its time in water and is such a powerful swimmer that it can be properly considered aquatic.
Snakes have become adapted to almost every environment including even the sea as this one has.
It doesnt often bite but it does have an extremely powerful venom so I am not going to handle it.
But I will help it a little with this stick.
As you can see it has a very flattened paddle at the end of its tail.
But on land its pretty helpless.
However if I assist it in getting into the sea And now its in its element.
Sea snakes have had to modify many of the features that enabled their far distant ancestors to colonise the land.
They still have a lung with which to breathe air like other snakes but they can also absorb oxygen from the seawater through their skin.
Salt inevitably gets into a sea snakes body but the snake manages to get rid of that by excreting it from a gland under its tongue.
It also needs to drink fresh water.
So in calm seas it waits at the surface for rain.
Sea snakes really are truly marine creatures.
They can live out here in the open ocean and the only clue you have to their link with the land is that they have to come up every quarter of an hour or so for a gulp of air.
Most sea snakes like this bar-bellied species hunt fish.
They have one of the most lethal venoms known which kills almost instantaneously.
And that is a very important quality if you hunt fast-swimming ocean-going prey.
But paradoxically the most highly specialised sea snake of all has abandoned venom altogether.
It has a beak like a turtle and a wholly different way of feeding.
Reef fish dont like to have it around.
They mob it.
It doesnt even retaliate.
Its not interested in them.
Its after their eggs.
These the fish have stuck to the stony branches of the coral.
The snakes hardened turtle-like top lip enables it to scrape them off.
Its such a slow-moving browser that algae and other small organisms grow on its skin as they do on the bottom of a boat.
The loss of limbs could seem to be a handicap and certainly makes the snakes seem alien creatures to us.
But it is that very loss that has enabled the snakes to colonise every environment from below the ground to above the ground from bushes to trees to the air and even to the sea.
And it is that absence of limbs too which has enabled them to do it with such elegance and grace.
Filming venomous snakes presented a lot of special problems to the Life in Cold Blood team but the toughest was trying to film a rattlesnake hunting in the wild.
A rattlesnake making a kill has rarely even been seen and never before filmed and for several reasons.
For one thing rattlesnakes are so well camouflaged theyre very difficult to find.
We enlisted the help of snake expert Harry Greene and his team.
Theyve been studying a group of timber rattlesnakes using radio telemetry which enables them to find their rattlesnakes at any time of day or night.
Most of us will never find them and theyre superbly camouflaged.
Exactly but thats been one of the wonderful things about radio telemetry is we can have an animal that we can dial up.
ATTENBOROUGH: To have any chance of success the crew had to be able to find the rattlesnakes on their own.
So producer James Brickell had to take a course in telemetry techniques himself.
Hmm point it a little bit more this way.
ATTENBOROUGH: Each snake has been implanted with a tiny transmitter.
If you dial its frequency you can pick up a beeping sound.
And that gets louder the nearer you get to the snake.
(BEEPING) And so its just like if you were trying to find your favourite rock-and-roll station or something but now were gonna find our favourite rattlesnake.
So you just punch in its number and its on the air.
ATTENBOROUGH: It sounds simple in theory but theres a snag.
(BEEPING) Its here somewhere.
just be really careful guys.
ATTENBOROUGH: In a forest the signal can bounce off trees and give you a false reading so that it can seem that the snake is everywhere.
And you dont want to think a reading is false and then tread on your snake by mistake.
Hes that way there? MAN: Youll find hes up there somewhere.
Lets find him.
james its starting to get dark.
Yeah I know.
Hes in there.
I reckon hes hunting.
MAN: James be careful where youre going.
ATTENBOROUGH: And it isnt just the one snake youre tracking.
There are dozens of others in the area that arent tagged.
(BEEPING CONTINUES) MAN: Follow my hand.
jAMES: There he is.
Its about 20 feet.
MAN: All right good.
jAMES: Six metres.
ATTENBOROUGH: And so at last the crew meet a very special snake called Hank.
Hank is in a perfect position for his ambush.
To film the action without disturbing him or his prey cameraman Mark MacEwen has fitted his camera with motion detectors from a burglar alarm.
They will turn on the camera without anyone having to be there.
So for the first time they set up their gear in front of a live snake.
They could now leave Hank and track another of Harrys snakes.
So that means you know individual snakes over a long period of time.
Do they differ very much? Absolutely absolutely.
Now there are species differences so certain rattlesnake species are more sort of nasty-tempered than others.
But even within a population youll have one that just never gets riled up and one that you know you just cant get too close to without it getting upset.
ATTENBOROUGH: With one camera set up on Hank james decides to track another snake and to do so in the dark which is when most rattlesnakes hunt.
But in the pitch blackness there was a distinct possibility that James would accidentally get so close to the snake he was looking for he would step within striking distance.
Quite unnerving if you havent done it before.
(BEEPING) Its actually pretty dangerous walking around in the middle of the night trying to find a rattlesnake in these conditions.
Hes really close.
Its got to be here over near these logs.
I think the snakes about probably five 1 0 metres away.
It would be easier to find a needle in a haystack than to find a reptile that looks like a load of dead leaves in a huge pile of dead leaves.
MARK ON RADIO: Have you found it, fellows? Negative Mark.
Weve got to a huge pile of logs and wood.
ATTENBOROUGH: The team decide to abandon tracking the second snake and instead check on the camera they had left on Hank in the afternoon.
I think its too dangerous actually to go poking around in there and anyway you wouldnt be able to get the lights and the camera in.
So were gonna wrap on it and come back.
Weve seen things on your videos weve never seen before.
-Really? -Which is kind of surprising.
I mean weve watched snakes a lot.
By we I mean all rattlesnake biologists and weve seen things on your videos we havent seen before.
So I think its actually kind of exciting to think about how this kind of collaboration might really be a feedback between the media and the public and science and so forth.
ATTENBOROUGH: And something very surprising had happened at our very first attempt and in broad daylight.
A chipmunk had tripped the motion detectors and Hank makes a kill right in front of the cameras.
-Weve got a strike.
-We got him.
-Already weve got it.
-We got it.
I thought you were winding me up.
MAN: I was like James somethings happened here.
I thought Well thats just a classic wind-up.
First night to get that.
ATTENBOROUGH: We hadnt got the eating shot but its a start.
And then the camera is set off again by a second chipmunk behaving very strangely.
We showed the recording to Harry and he was fascinated.
HARRY: Now what was that chipmunk doing? Was it perceiving something that the other chipmunk left some kind of alarm odour or something? Was it perceiving the odour of the rattlesnake? Or was it something I cant even imagine yet? But something was going on there that I didnt know to expect anyway.
And its in your film.
ATTENBOROUGH: Hank could clearly be the star of the show so the crew decide to concentrate all their efforts on him and to track him for two weeks around the clock.
They quickly learn that despite his ability to hurt one of them very seriously he seems pretty unconcerned.
In fact he never even rattles a warning at them.
(BEEPING) The more they get to know him the more they think theyve got a good chance of filming another hunt.
But then there is a serious problem.
NEWSCASTER: Its just been raining here non-stop for the past three days, and they say that Tuesday afternoons hard rainstorm was the straw that broke the camels back.
ATTENBOROUGH: Just as things are looking so promising New York State has its worst floods for a decade and all filming comes to a standstill.
As you can see the weather is awful.
Wont affect the rattlesnake at all.
Hes perfectly happy.
Hell be sat down in here somewhere just waiting but it does affect the mammals.
The chipmunks and the mice theyll just be hunkered down somewhere not doing anything very much.
And it affects us but hell be fine.
Its just we cant film anything so its just a matter of waiting now.
ATTENBOROUGH: After tracking him in the rain for 1 0 days theres a break in the weather and Hank starts hunting again.
He chooses a position for an ambush in a very accessible spot.
The team has another chance to use their remote cameras this time operating in night vision.
MAN: James just be careful where you come in.
Dont go that way.
I think thats the direction hes headed in.
Youve got something have you? MAN: Mate weve got him hitting a mouse in the middle of frame and swallowing it.
ATTENBOROUGH: This time they get more than the strike.
This time Hank decides to eat his dinner very obligingly right in front of the camera.
Mate that is the most incredible piece of behaviour you have ever seen.
ATTENBOROUGH: So after two weeks and a lot of effort they succeed in capturing a crucial and intimate moment in the life of this very special snake.
People dont automatically love snakes most of them dont.
And yet if you can show them things about the lives of these animals that impress them with the fact these are animals with complex daily activities These arent things that are waiting around for an opportunity to kill people.
When you tell people things like that then they get drawn in.
And hopefully when we show them your films theyll be drawn in.
Well youve drawn me in.
Thank you very much.
HARRY: Pleasure.
ATTENBOROUGH: And when I get to see the footage its fair to say that Im just as knocked sideways as the crew had been.
(GASPING) Theres the mouse.
(ATTENBOROUGH EXCLAIMS) Oh my goodness.
Yes.
Thats a dead mouse all right.